Method for preparing a working electrode

Abstract

The present invention relates to a method for the preparation of a working electrode, the method comprising application of a sensing material in several steps. Further, the present invention relates to an analyte sensor comprising the working electrode as well as to the use of the analyte sensor for detecting at least one analyte in a sample.

1 . A method for manufacturing a working electrode of an analyte sensor is provided, wherein the method comprises the following steps:
 (a) providing a substrate comprising
 a first side and a second side, 
 at least one conductive material positioned on the first side of the substrate, 
   (b) applying a sensing material to an application area on the first side of the substrate, and   (c) obtaining the working electrode of the analyte sensor on the first side of the substrate, wherein the sensing material comprises
 at least one enzyme and 
 at least one cross-linker, 
   wherein the sensing material is applied in step (b) in a wet layer thickness of greater than about 20 μm in a single application, wherein step (b) is carried out via cannula-coating.   
     
     
         2 . The method of  claim 1 , wherein step (b) is performed only once. 
     
     
         3 . The method of  claim 1 , wherein the at least one conductive material positioned on the first side of the substrate is selected from gold, carbon, carbon paste and any combination thereof. 
     
     
         4 . The method of  claim 1 , wherein the sensing material comprises at least chemical crosslinker, particularly PEGDGE 500. 
     
     
         5 . The method of  claim 1 , wherein the at least one crosslinker is present in the sensing material in an amount up to about 25% (w/w), particularly of about 0.5% (w/w) to about 25% (w/w) based on the dry weight of the sensing material. 
     
     
         6 . The method of  claim 1 , wherein
 (i) the cannula has an inner diameter of about 0.3 mm to about 0.4 mm, particularly about 0.33 mm; and/or   (ii) the speed of the substrate relative to the cannula during step (b) is in the range from about 1 mm/s to about 20 mm/s, particularly in the range from about 2 mm/s to about 15 mm/s, e.g. about 8 mm/s, and/or   (iii) the flow rate of the sensing material during step (b) is in the range from about 0.007 ml/min to about 0.05 ml/min, preferably in the range from about 0.01 ml/min to about 0.03 ml/min, particularly of about 0.015 ml/min, and/or   (iv) the distance between the cannula and the surface of the first side of the substrate to which the sensing material is applied during step (b) is in the range from 50 μm to about 100 μm, particularly about 70 μm.   
     
     
         7 . The method of  claim 1 , wherein after step (b) the sensing material is dried. 
     
     
         8 . The method of  claim 1 , wherein after drying the sensing material of the working electrode has a dry total thickness in the range from about 3 μm to about 8 μm, particularly from about 3 μm to about 6 μm and more particularly from about 4 μm to about 5 μm. 
     
     
         9 . The method of  claim 1 , which is carried out continuously, particularly wherein the substrate is a raw substrate material, particularly a sheet or a roll onto which the layer of sensing material is applied. 
     
     
         10 . A method for manufacturing an analyte sensor comprising manufacturing a working electrode according to  claim 1  and providing at least one further electrode. 
     
     
         11 . An analyte sensor comprising:
 (i) a substrate comprising
 a first side and a second side, and 
 at least one conductive material positioned on the first side of the substrate, 
   (ii) a working electrode comprising a sensing material, which at least partially covers the first side of the substrate,   wherein the sensing material forms a layer on the first side of the substrate, wherein the layer of sensing material comprises edges generated by the application of the sensing material onto an application area on the substrate,   wherein the sensing material comprises at least one enzyme and optionally at least one crosslinker,   wherein the layer of sensing material has a dry average total thickness in the range from about 3 μm to about 8 μm, particularly from about 3 μm to about 6 μm and more particularly from about 4 μm to about 5 μm,   and wherein the dry total thickness of the layer of sensing material along at least one of said edges is substantially the same or is increased compared to the dry average total thickness of the layer of the sensing material.   
     
     
         12 . The analyte sensor of  claim 11 , wherein the dry total thickness of the sensing material at least along one of the edges of the application area, particularly along all edges of the application area, is at least about 75% and up about 125% compared to the dry average total thickness of the layer of the sensing material (being defined as 100%), or
 wherein the dry total thickness of the sensing material at least along one of the edges of the application area, particularly along all edges of the application area, is at least about 125% compared to the dry average total thickness of the layer of the sensing material (being defined as 100%).   
     
     
         13 . The analyte sensor of  claim 11  comprising at least one further electrode, particularly precisely one further electrode, particularly wherein the at least one further electrode is selected from a counter electrode, a reference electrode and a combined counter/reference electrode. 
     
     
         14 . The analyte sensor of  claim 11 , which is a two-electrode sensor comprising precisely one working electrode and precisely one combined counter/reference electrode. 
     
     
         15 . Use of an analyte sensor of  claim 11  for detecting at least one analyte in a sample.